Recently, according to the improvement of performance of image forming apparatuses such as a digital copying machine, an integrated digital apparatus having not only a copying function but also a function of a printer is developed and spread. As a secondary function of such image forming apparatuses, a technique for keeping security of sheets is known.
A Patent Document 1 (JP-A-2005-107057) discloses a technique for managing paper by adding, at the time of copying, a storing member that stores identification information separately from visible information to at least one of sheets at a copy source and a copy destination.
However, in this Patent Document 1, since the sheets are made physically bulky by the addition of the storing member, it is hard to handle the sheets. Further, because of a physical operation for adding the storing member at the time of mounting of the same, there is a problem in that, for example, a jam of paper or an error such as un-mounting of the storing unit may occur or the storing member once added may be lost.